In the recent years there has been a significant proliferation in the number of wireless applications that have been deployed, and along with the more traditional services, this has placed a significant amount of pressure on sharing the available radio spectrum.
Use of the RF spectrum is regulated by governmental entities in most countries. Currently, there are dedicated or licensed portions as well as unlicensed portions of the communications spectrum. Certain bands of the spectrum may be overloaded, such as cellular network bands, while other bands may be underused, such as television and radio broadcast bands. For example, because the unlicensed bands of the spectrum may be accessed freely, these bands tend to be heavily used. In contrast, recent studies indicate that only a small portion of the licensed (regulated) bands is being used. For example, a town may have only a few television stations or a radio or TV station may cease broadcasting at a certain time of day. Until recently, non-licensed users were prevented from using such underused bands of the spectrum.
This, together with the evolution of the TV broadcast from analog to digital, had lead regulatory bodies in some countries to open up some bands of the RF spectrum to secondary users, provided such secondary users avoid interference with primary users. In the United States, the Federal Communication Commission (FCC) mandated transition from analog to digital television by June 2009, which resulted in all full-power TV broadcast be consolidated below channel 52. As each TV station operating in a certain geographic region/area uses only a limited number of channels from the TV band, some digital channels remain unused in the respective area: this locally available spectrum is called “white space”.
Few developments are underway with a view to creating a regulated environment for using the available TV spectrum.
In response to a Notice of Proposed Rule Making (Notice) issued by the U.S. FCC in May 2004, which proposed to allow unlicensed operation in the TV bands at locations where frequencies are not in use by licensed services, the IEEE created in October 2004 the Wireless Regional Area Networks Working Group. The mandate of this Working Group is to develop a new standard, called IEEE 802.22 for operation of license-exempt devices on a non-interfering basis in spectrum that is allocated to the TV Broadcast Service. Draft v3.0 of the standard is now available.
At the same time, the IEEE 802.19 Wireless Coexistence Working Group has begun developing standards for coexistence between wireless standards of unlicensed devices. These standards will define recommended wireless coexistence metrics and methods for computing them, as well as various wireless coexistence scenarios. The group is debating topics like: information needed from TV white space devices, also known as TVBD, and networks, interfaces and communication between TVBDs and TVBD networks, coexistence mechanisms, coexistence decision making entities, decision making topologies.
In November 2008, the FCC released its Second Report and Order (FCC R&O) with rules allowing a new class of unlicensed consumer electronics products to operate in the broadcast television spectrum at locations where the spectrum is not being used by licensed services. This unused TV spectrum is often termed “white space”. These forthcoming products have previously been referred to as white space devices, but are now called TV band devices (TVBDs).
The new FCC R&O rules allow the development of new and innovative types of unlicensed devices that provide broadband data and other services for businesses and consumers without disrupting the incumbent television and other authorized services that operate in the TV bands.
The new rules provide for operation of two types of unlicensed TVBD, namely fixed devices and personal/portable devices. Thus, Title 47: “Telecommunication Part 15 Radio Frequency devices”, Subpart H—Television Band Devices” sets out the regulations for TVBDs which are unlicensed intentional radiators operating on available channels in the broadcast television frequency bands at 54-60 MHz, 76-88 MHz, 174-216 MHz, 470-608 MHz and 614-698 MHz bands. This document defines a “fixed device” as a TVBD that transmits and/or receives radio-communication signals at a specified fixed location using relatively high power and could be used to provide a variety of services including wireless broadband access in urban and rural areas. The fixed devices may operate as part of a system, transmitting to one or more fixed TVBDs or to personal/portable TVBDs. The personal/portable devices will use relatively low power and could, for example, take the form of devices such as Wi-Fi-like cards in laptop computers or wireless in-home local area networks (LANs).
This Document also defines a Mode II operation for a personal/portable TVBD, whereby the device determines the available channels at its location using its own geo-location and TV bands database access capabilities. TVBDs operating in Mode II may function as master devices. Devices operating in Mode I do not require use of a geo-location capability or access to the TV bands database, and require operation under control of a master device (they operate in client mode).
Initially, the idea was for all TVBDs to use spectrum sensing to detect which frequencies are in use and avoid them, but FCC ruled that spectrum sensing is not sufficient by itself to enable unlicensed devices to reliably determine the TV channels that are available for use at a location and now the plan is to combine a database service with spectrum sensing to protect incumbent services from interference from TVBDs. Also, a fixed or a personal portable unlicensed TVBD should access the database over the Internet and provide it with its location. The database system will then determine which television channels are available for use by the TVBD at that location, based on the information in the database, and return a list of these channels to the respective TVBD. The database should also register unlicensed fixed devices and record appropriate information about them, including the devices location and user contact information. In addition, unlicensed fixed devices and unlicensed personal portable devices operating in Mode II are required to use spectrum sensing to identify any digital or analog TV services, wireless microphone activity and any other protected signals that use the TV spectrum in the respective geographical area but do not appear in the database.
The information stored in this database would include the numbers of the protected channels, geo-location and channel contours of each TV tower and each stadium or a site using wireless microphones, and terrain elevation for the service region, maximum EIRP for the licensed TV channel, antenna height and gain, propagation models, interference scenarios. The information in the database would also include identification and geo-location information for the fixed TVDBs in the service area, their transmission power and operating channels, etc. It is expected that the type and extent of information stored in the database will be agreed upon by broadcasters, regulators and service providers, and will be updated regularly. The database should be pulled by the TVBDs or pushed to the TVBDs. The term “system information” is used to designate the information stored in the informational database.
The TVBD providers and devices, which are the database users, shall provide their configuration/transmission parameters to the database, together with any sensed data regarding the presence of a primary service they may have identified (sensed, detected) in that area. As users of the database, these entities must be validated (authentication and authorization) upon requesting database access. The information uploaded by these users is submitted to a validation and security verification process; the broadcasters and regulators shall confirm the data before updating the database. TVBD, particularly base station transceivers (BTS) and access points (AP), shall access the database to acquire the protected channel information, available channel information, interference status, power limitation data, etc, which is used for configuring the spectrum usage, and for conveying this information to any TV band device under their control. Each time when an AP or BTS receive updates from the database, these TVBD shall reconfigure the spectrum information quite fast (e.g. within 30 seconds). For example, when a broadcaster decides to use a channel, that channel must be cleared within this time frame.
Broadcasters and regulators may push the updates to all TVBDs in the service area either directly or via the TV WS service providers. Preferably, the TV WS service providers shall provide an anchor point where the database server can push data to. Broadcasters and regulators may push/update a particular data type to clear a channel or multiple channels of a region within a certain amount of time delay.
Databases with information for wireless communication networks are known. One example of such a database is disclosed in U.S. Pat. No. 6,301,477 (Lennert, et al.) issued on Oct. 9, 2001, entitled “Method for creating and modifying similar and dissimilar databases for use in GSM wireless configurations for telecommunication systems”. Lennert et al. disclose an automatic database creation and modification method used in three circumstances: during the testing of a network device (e.g. a switch), when the device is sold to a customer and needs to be configured with customer's specifications and when a device experiences a full failure. Under any of these circumstances, a new database is created and is populated with data retrieved from preexisting source GSM wireless network databases. The data mentioned in the patent includes information concerning home location register, base station interface, location areas, geographical locations, operations maintenance and billing center interfaces, visitor location register, etc.
Spectrum Bridge Inc., website: http://spectrumbridge.com, is one of the active companies involved in the TV white space database development. The company views the TV spectrum as an asset which can be traded among users and developed software products to enable this functionality. The proposed solution is a centralized database service, called Universal Spectrum Access, which can be used as an add-on feature to help existing wireless communication equipments. The service takes a “coordination of network resources and operations” standpoint. The database contains information from FCC's Universal Licensing System and has additional information such as spectrum availability, location and bandwidth, geographic information such as spectrum license boundaries, census block sizes, tower locations and protected incumbent zones, census and market population data, spectrum service rules. The service issues spectrum certificates to users on specific frequency, power output, channel plan and time period.
In a document entitled: “Proposal by Google Inc. to provide a TV band device database management solution” submitted in January 2010 before the Federal Communication Commission, ET Docket No. 04-186, Google Inc. proposes the basic functional architecture for a TV white space (TVWS) database, including data repository, registration, and determination of available channels/query process. According to this proposal, the TVWS database should serve as a repository of three primary categories of information: (1) information about protected facilities, as recorded in FCC databases; (2) information about facilities that are not recorded in FCC databases but are otherwise entitled to protection provided they register with the TVWS database; and (3) identification and location information of registered Fixed and Mode II (mobile) TVBDs. Google's document includes proposals for repository and registration functions, and query functions associated with the database. The proposal also provides a basis for a process to support synchronization with other TVWS databases with a view to exchange information, on a set interval, about new, modified or deleted database records.
Although the US FCC's Second Report and Order pretty much lays out what are presumably the data fields to be used, there still doesn't seem to be a full consensus on how many entities should be recruited for the database network, what specific roles they should play and what architecture model the database should follow. FCC has not mandated a specific architecture to manage the required collection and dissemination of data needed for TVBDs. Furthermore, current proposals for a TV white space database have a centralized database approach in which all the pertinent information is stored in a central database.